Goitrogens and Thyroid Conditions: Risk or Rubbish?

By: Stacy Kennedy, MPH, RD, CSO, LDN; Reboot Nutritionist

If you have an underactive thyroid or take thyroid medication, chances are you have a lot of unanswered questions about the best diet to follow*. With 20 million Americans suffering from some form of thyroid disease, and as many as 60% unaware of their condition, you’re certainly not alone. The internet can be a minefield of contradictory recommendations for which foods to include, which to avoid and what supplements to take. What does the actual scientific evidence suggest? As with most nutrition topics, the answer is much more complex than it may seem.

What Are Goitrogens?

Goitrogens are naturally occurring compounds in certain plant foods that have the potential to disrupt thyroid function. In preliminary animal studies, exposure to pro-goitrogenic food substances led to increased losses of iodine in urine, enlargement of the thyroid gland (goiter) and significantly decreased levels of circulating T4 and T3 levels (active thyroid hormones). In humans, it’s suspected that goitrogens could interfere or block enzymes that allow the thyroid to properly use iodine. Iodine is required for the formation of thyroid hormones.

Which Foods Are Goitrogenic?

Foods in the goitrogenic group include many cruciferous veggies as well as unfermented soy foods (like edamame and tofu). However, cooking these foods breaks down the compounds that have caused concern. I suggest that those with thyroid issues consume crucifers cooked, like lightly steamed, roasted, grilled or baked. Limit or avoid juicing and blending raw cruciferous vegetables.

Cruciferous veggies like kale, broccoli, cauliflower, cabbage, radish, bok choy, collard greens, mustard greens, arugula (rocket), watercress and Brussels sprouts are healthy, with nutrients to support the body’s natural detoxification processes and provide cancer-fighting compounds.

Certain soy foods may not be ideal for underactive thyroid sufferers either. I recommend limiting the consumption of highly processed soy, like soy powders, meatless burgers and other packaged foods listing “isolated soy protein” or “soy protein isolate” in the ingredients. Including some organic edamame on your salad is fine on occasion, and is a great source of fiber and protein.

Keep in mind these are suggestions and general guidelines. The jury is still out, meaning there is not sufficient evidence to suggest that everyone with a thyroid condition forgo kale salads. It’s best to check with your doctor and nutritionist about your personal risks or benefit.

Since many of these dietary suggestions are considered preliminary or not completely evidence based, as research is still emerging, don’t feel like you have to be all or nothing. For example, next time you’re at your friend’s house for dinner, if there’s some raw kale and broccoli mixed into the green salad everyone’s eating, no need to pass it up. But day to day, consuming large amounts of these raw foods, like we do in juicing, may be something to modify, especially if you’re continuing to experience symptoms of underactive thyroid like resistant weight loss, feeling cold and fatigued, tired and sluggish.

Is Iodine an Issue?

Iodine deficiency is rare in the US, mainly due to fortification in salt and our overconsumption of sodium. Pregnant women may be more at risk and should consult with their physician about taking a supplement. Low levels of urinary iodine, (a marker for iodine intake), were on the rise in the US in the 1980s and 90s, but data from 2000 indicates that this decline has leveled off and remains in the “iodine sufficient” range.

However, more recently, concerns have been raised as health-minded individuals seek alternatives like Himalayan salt, sea salt and Celtic salt which are not required to be fortified with iodine, so there’s a concern that those using non-fortified cooking salts might not be getting enough dietary iodine.

Iodine deficiency is certainly a concern across the globe with more than 50 countries identified as having populations that are iodine-deficient. In Australia and in New Zealand for example, iodine deficiency is an issue. Certain regions have higher prevalence of concern, due to lack of adequate iodine in the soil, like New South Wales and Victoria, where 60% of Australia’s population lives.

What Should I Eat More Of?

Including minerals that may be lacking in soil or in the diet, such as selenium and iodine, may be helpful for metabolism, energy level and overall immunity.

Selenium rich foods include Brazil nuts (studies suggest that 5 nuts per day is the optimal “dose”), sunflower seeds, fish, shellfish, mushrooms, onions, whole grains (wheat germ, brown rice, barley, oats), eggs, poultry and beef. Iodine-rich foods include seaweed, fish, fortified table salt, and dairy products.

Switch up your greens. When juicing, making massive salads or blending up smoothies, rather than an all-kale-all-the-time mantra, go for variety. This not only helps limit over-exposure to compounds of concern but also allows you the benefit of eating and drinking the rainbow and getting a broader spectrum of nutrients unique to each veggie.

Here’s a sample of swaps you can make for raw veggies:

Instead of this:                                                  Eat or juice this:

Kale Swiss Chard
Collard/Mustard Greens Romaine
Bok Choy Green Leaf Lettuce
Broccoli Cucumber
Arugula Spinach
Radish Beet
Cauliflower Fennel
Turnip Parsnip
Watercress Parsley
Green Cabbage Celery
Red Cabbage Red Leaf Lettuce

*If you have a hypothyroid condition, including Hashimoto’s autoimmune disease, then consider signing up for our next 60-Day Guided Reboot for Thyroid. This program will help you learn how to properly nourish and protect your thyroid, lose weight (if you have weight to lose), support a healthy immune system and jumpstart a healthy lifestyle. Register today.

Here are some delicious, thyroid-friendly juices to try:

Thyroid-Friendly Greens and Carrot Juice

Chard Rock Café Juice

When Life Gives you Lemons

Sweet Pear Turmeric Juice

Calcium Rich Green Juice

Thyroid-Friendly Mediterranean Juice

Looking to take control and manage your thyroid condition? Sign up for our next 60-Day Guided Reboot for Thyroid — this program will help you get your body back into balance. You’ll learn to make lifestyle changes that can assist in improving overall wellness, and get help with certain thyroid-related issues such as excess weight.

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Stacy Kennedy, MPH, RD, CSO, LDN; Reboot Nutritionist

Stacy is a Board Certified Specialist in Oncology Nutrition and an Integrative Nutritionist. She consults for various companies, focusing on health, wellness and innovative strategies to help increase individual’s fruit and vegetable intake. Stacy is an American College of Sports Medicine Certified Health Fitness Specialist; she holds a BS degree in Dietetics from Indiana University, completed her dietetic internship at Massachusetts General Hospital, and earned a Masters in Public Health from the University of North Carolina at Chapel Hill. She is a Senior Clinical Nutritionist at the Dana Farber Cancer Institute/Brigham & Women’s Hospital, Harvard Medical School teaching affiliates, in Boston, MA, with more than 20 years of experience. Stacy created and now serves as project manager and lead writer for nutrition services content on the Dana Farber website and the affiliated, nationally recognized nutrition app. Stacy is regularly featured on TV, radio, print and social media on behalf of Dana Farber and other organizations. Together with her husband, Dr. Russell Kennedy PsyD, they have a private practice, Wellness Guides, LLC. Stacy is an adjunct professor in Wellness and Health Coaching at William James College, currently teaching a graduate course in Health Coaching. Stacy is featured in the award winning documentary films, “Fat, Sick & Nearly Dead” and “Fat, Sick & Nearly Dead 2,” and serves on the Reboot with Joe Medical Advisory Board. Stacy lives in Wellesley with her husband, two sons and three dogs. She enjoys cooking, yoga, hiking and spending time with friends and family. Stacy is also one of the nutritionists who runs our Guided Reboot programs.

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